An emerging syndrome of fat redistribution called lipodystrophy (LD) which consists, in part, of abdominal obesity is being reported with increasing frequency in persons with HIV infection. Although it is usually noted in association with the class of antiretroviral drugs, protease inhibitors, the cause and mechanism of this syndrome are unclear. Subclinical insulin resistance also occurs frequently with the protease inhibitors, and has been found relatively soon after these medications are begun. Therefore, insulin resistance may be causing or contributing to the development of LD. Because protease inhibitores should usually not be discontinued in the presence of virologic success, and because chronic consequences of abdominal obesity are well-established, other treatment for LD is needed. This is a 6-month placebo-controlled randomized clinical trial of metformin hydrochloride, an oral diabetic medication, 1.5 grams daily, for HIV-associated LD. All participants will also receive individual nutritional counseling to reduce the glycemic index of their diets. The primarily endpoint is the reduction of abdominal adiposity measured by CT scan; secondary endpoints include improvements in serum triglycerides and HDL cholesterol levels.